Axles and pinions of work vehicles, such as tractors and construction equipment, generate considerable friction and heat during use. As a result, such work vehicles include a lubrication system which circulates a lubricating fluid, such as oil, from a reservoir to the interior of a housing about the axle and which returns excess oil from the interior of the housing to the reservoir. Such lubrication systems typically include a dedicated gear pump which supplies lubricating fluid to the housing extending about the axle. Such lubrication systems typically use one of two methods to remove excess fluid from the housing and to return the excess fluid to the reservoir. One method employs an additional dedicated gear pump which pumps excess oil from the housing and returns the excess fluid to the reservoir. Another method employs an additional dedicated gear pump to pump air into the fluid so as to aerate the fluid prior to the fluid entering the housing about the axle. The aerated fluid adds to the air volume in the axle housing to force excess oil through a drain line back to the fluid reservoir.
Although such lubrication systems have been commonly employed for several years, such lubrication systems have several drawbacks associated with the additional required gear pump necessary to pump excess oil out of the axle housing or to pump air into the fluid to aerate the fluid prior to entering the axle housing. First, the additional gear pump is expensive and space consuming. Second, operation of the additional gear pump requires additional power which increases the operating cost of the work vehicle. Third, operation of the additional gear pump creates excessive undesirable noise.
Thus, there is a continuing need for an axle lubrication system that provides appropriately pressurized fluid for axle lubrication and which removes excess fluid from the axle housing while eliminating the additional gear pump and associated power, noise and operating costs.